Sliding patio doors typically include a stationary panel and a horizontally movable panel, each including a surrounding frame. The frames are spaced one behind the other to permit sliding of one relative to the other. Spacing is necessary for sliding, but is detrimental to effective closure of the door, and so these doors usually are not as airtight or weathertight as desired. The conventional solution to this is weather stripping on one or both frame members along the length of their juncture. This has been only a partial solution.
In addition to spacing of the panels required for slidability, the frame members are, over time, subject to warping or other deflection from weight of the glass or other causes. This can aggravate the already the already inherent tendency for these doors to leak air. Where warping is involved, weather stripping, especially if it is originally installed weather stripping, is of little or no effect and can be remedied only by supplemental weather stripping put on over the old, or new weather stripping put on in its place.
The alternative to weather stripping to improve the airtight effectiveness of sliding doors is to minimize or eliminate the clearance between panels when the door is closed. U.S.Pat. No. 3,060,487 to Baiter discloses a sliding window arrangement having a contact member which pushes one window panel in against the other where they overlap. To exert this push, the contact member must of necessity be mounted on a support or frame external of the window panel themselves. The device is therefore limited to use at the top or bottom of the window, and does not produce effective closure between top and bottom.
The movable panel of a patio door slides back and forth on tracks within a frame. Clearance between the movable panel and the top of the frame allows for installation and removal of the panel. This is a potential security problem because burglars and thieves can also remove the movable panel.
One object of this invention is to provide a positive clamping of one patio door panel to the other at one or more points between top and bottom to enhance the airtight effectiveness of the door.
Another object is to provide positive locking of the panel of a patio door to prevent their disengagement by either horizontal or vertical movement.
Another object is to provide such a locking system which is capable of simple retro-installation.